The EXTRA record allows for additional space to be allocated
beyon what is currently reserved.  Add code to emit and read
this record type.

Nothing uses extra space yet.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/signal.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 51 insertions(+), 4 deletions(-)

diff --git a/linux-user/signal.c b/linux-user/signal.c
index f9eef3d753..ca0ba28c98 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -1443,6 +1443,15 @@ struct target_fpsimd_context {
     uint64_t vregs[32 * 2]; /* really uint128_t vregs[32] */
 };
 
+#define TARGET_EXTRA_MAGIC  0x45585401
+
+struct target_extra_context {
+    struct target_aarch64_ctx head;
+    uint64_t datap; /* 16-byte aligned pointer to extra space cast to __u64 */
+    uint32_t size; /* size in bytes of the extra space */
+    uint32_t reserved[3];
+};
+
 struct target_rt_sigframe {
     struct target_siginfo info;
     struct target_ucontext uc;
@@ -1502,6 +1511,15 @@ static void target_setup_fpsimd_record(struct target_fpsimd_context *fpsimd,
     }
 }
 
+static void target_setup_extra_record(struct target_extra_context *extra,
+                                      uint64_t datap, uint32_t extra_size)
+{
+    __put_user(TARGET_EXTRA_MAGIC, &extra->head.magic);
+    __put_user(sizeof(struct target_extra_context), &extra->head.size);
+    __put_user(datap, &extra->datap);
+    __put_user(extra_size, &extra->size);
+}
+
 static void target_setup_end_record(struct target_aarch64_ctx *end)
 {
     __put_user(0, &end->magic);
@@ -1554,14 +1572,16 @@ static void target_restore_fpsimd_record(CPUARMState *env,
 static int target_restore_sigframe(CPUARMState *env,
                                    struct target_rt_sigframe *sf)
 {
-    struct target_aarch64_ctx *ctx;
+    struct target_aarch64_ctx *ctx, *extra = NULL;
     struct target_fpsimd_context *fpsimd = NULL;
+    uint64_t extra_datap = 0;
+    bool used_extra = false;
 
     target_restore_general_frame(env, sf);
 
     ctx = (struct target_aarch64_ctx *)sf->uc.tuc_mcontext.__reserved;
     while (ctx) {
-        uint32_t magic, size;
+        uint32_t magic, size, extra_size;
 
         __get_user(magic, &ctx->magic);
         __get_user(size, &ctx->size);
@@ -1570,7 +1590,12 @@ static int target_restore_sigframe(CPUARMState *env,
             if (size != 0) {
                 return 1;
             }
-            ctx = NULL;
+            if (used_extra) {
+                ctx = NULL;
+            } else {
+                ctx = extra;
+                used_extra = true;
+            }
             continue;
 
         case TARGET_FPSIMD_MAGIC:
@@ -1580,6 +1605,17 @@ static int target_restore_sigframe(CPUARMState *env,
             fpsimd = (struct target_fpsimd_context *)ctx;
             break;
 
+        case TARGET_EXTRA_MAGIC:
+            if (extra || size != sizeof(struct target_extra_context)) {
+                return 1;
+            }
+            __get_user(extra_datap,
+                       &((struct target_extra_context *)ctx)->datap);
+            __get_user(extra_size,
+                       &((struct target_extra_context *)ctx)->size);
+            extra = lock_user(VERIFY_READ, extra_datap, extra_size, 0);
+            break;
+
         default:
             /* Unknown record -- we certainly didn't generate it.
              * Did we in fact get out of sync?
@@ -1595,6 +1631,9 @@ static int target_restore_sigframe(CPUARMState *env,
     }
     target_restore_fpsimd_record(env, fpsimd);
 
+    if (extra) {
+        unlock_user(extra, extra_datap, 0);
+    }
     return 0;
 }
 
@@ -1621,7 +1660,8 @@ static void target_setup_frame(int usig, struct target_sigaction *ka,
                                CPUARMState *env)
 {
     int size = offsetof(struct target_rt_sigframe, uc.tuc_mcontext.__reserved);
-    int fpsimd_ofs, end1_ofs, fr_ofs;
+    int fpsimd_ofs, end1_ofs, fr_ofs, end2_ofs = 0;
+    int extra_ofs = 0, extra_base = 0, extra_size = 0;
     struct target_rt_sigframe *frame;
     struct target_rt_frame_record *fr;
     abi_ulong frame_addr, return_addr;
@@ -1641,7 +1681,14 @@ static void target_setup_frame(int usig, struct target_sigaction *ka,
 
     target_setup_general_frame(frame, env, set);
     target_setup_fpsimd_record((void *)frame + fpsimd_ofs, env);
+    if (extra_ofs) {
+        target_setup_extra_record((void *)frame + extra_ofs,
+                                  frame_addr + extra_base, extra_size);
+    }
     target_setup_end_record((void *)frame + end1_ofs);
+    if (end2_ofs) {
+        target_setup_end_record((void *)frame + end2_ofs);
+    }
 
     /* Set up the stack frame for unwinding.  */
     fr = (void *)frame + fr_ofs;
-- 
2.14.3

On 16 February 2018 at 21:56, Richard Henderson
<richard.henderson@linaro.org> wrote:
> The EXTRA record allows for additional space to be allocated
> beyon what is currently reserved.  Add code to emit and read
> this record type.
>
> Nothing uses extra space yet.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---

> @@ -1554,14 +1572,16 @@ static void target_restore_fpsimd_record(CPUARMState *env,
>  static int target_restore_sigframe(CPUARMState *env,
>                                     struct target_rt_sigframe *sf)
>  {
> -    struct target_aarch64_ctx *ctx;
> +    struct target_aarch64_ctx *ctx, *extra = NULL;
>      struct target_fpsimd_context *fpsimd = NULL;
> +    uint64_t extra_datap = 0;
> +    bool used_extra = false;
>
>      target_restore_general_frame(env, sf);
>
>      ctx = (struct target_aarch64_ctx *)sf->uc.tuc_mcontext.__reserved;
>      while (ctx) {
> -        uint32_t magic, size;
> +        uint32_t magic, size, extra_size;
>
>          __get_user(magic, &ctx->magic);
>          __get_user(size, &ctx->size);
> @@ -1570,7 +1590,12 @@ static int target_restore_sigframe(CPUARMState *env,
>              if (size != 0) {
>                  return 1;
>              }
> -            ctx = NULL;
> +            if (used_extra) {
> +                ctx = NULL;
> +            } else {
> +                ctx = extra;
> +                used_extra = true;
> +            }
>              continue;
>
>          case TARGET_FPSIMD_MAGIC:
> @@ -1580,6 +1605,17 @@ static int target_restore_sigframe(CPUARMState *env,
>              fpsimd = (struct target_fpsimd_context *)ctx;
>              break;
>
> +        case TARGET_EXTRA_MAGIC:
> +            if (extra || size != sizeof(struct target_extra_context)) {
> +                return 1;
> +            }
> +            __get_user(extra_datap,
> +                       &((struct target_extra_context *)ctx)->datap);
> +            __get_user(extra_size,
> +                       &((struct target_extra_context *)ctx)->size);
> +            extra = lock_user(VERIFY_READ, extra_datap, extra_size, 0);
> +            break;
> +
>          default:
>              /* Unknown record -- we certainly didn't generate it.
>               * Did we in fact get out of sync?
> @@ -1595,6 +1631,9 @@ static int target_restore_sigframe(CPUARMState *env,
>      }
>      target_restore_fpsimd_record(env, fpsimd);
>
> +    if (extra) {
> +        unlock_user(extra, extra_datap, 0);
> +    }

This will fail to call unlock_user if the function returns early
(eg because of failed magic-number checks or the FPSIMD record
not being present).

You don't need the "if (extra)" check -- unlock_user() is
specified to do nothing if passed a NULL host_ptr.

Otherwise looks good.

thanks
-- PMM